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A very short uranium-uranium bond: the predicted metastable U(2)2+
Laura Gagliardi1, Pekka Pyykkö, Björn O Roos
1Dipartimento di Chimica Fisica F. Accascina, Università degli Studi di Palermo, Viale delle Scienze-Parco d'Orleans II, Palermo, Italy. laura.gagliardi@unipa.it
Physical Chemistry Chemical Physics : PCCP
|June 18, 2005
Summary
Quantum chemical calculations reveal that the U(2)2+ system exhibits numerous electronic states with a shorter bond length than neutral U2. Coulomb explosion to U+ ions is energetically feasible but requires overcoming a significant energy barrier.
Area of Science:
- Quantum chemistry
- Relativistic quantum mechanics
- Computational physics
Background:
- Uranium (U2) is a heavy element dimer with complex electronic properties.
- Understanding the electronic states and bonding of U2 is crucial for nuclear materials science.
Purpose of the Study:
- To investigate the electronic structure and stability of the U(2)2+ cation.
- To determine the bond length and energy landscape of U(2)2+.
Main Methods:
- Multiconfigurational quantum chemical calculations were employed.
- Relativistic effects were incorporated into the wave function calculations.
- Potential energy surfaces were analyzed to understand electronic states and dissociation pathways.
Main Results:
- A large number of low-lying electronic states were identified for U(2)2+.
- These states exhibit a significantly shorter bond length (approx. 2.30 Å) compared to neutral U2 (2.43 Å).
- The Coulomb explosion to form two U+ ions is energetically favorable (1.6 eV lower) but faces a broad activation barrier.
Conclusions:
- The U(2)2+ cation is electronically rich with diverse low-lying states.
- The shorter bond length suggests stronger bonding in the dication compared to the neutral dimer.
- Dissociation via Coulomb explosion is possible but kinetically hindered, indicating potential stability for the U(2)2+ species.